Flame-spraying powdery repair mixture

ABSTRACT

A flame spray mending material effective for applying a dense thermal spray mending layer to a silica brick wall of an industrial furnace, having a high crystallization ratio immediately after thermal spraying in a broad thermal spray condition, having an oxide concentration of 89% by weight or more of SiO 2 , more than 2.0 to 4.0% by weight of Na 2 O and/or more than 0.2 to 4.0% by weight of Li 2 O, having a 80% or more crystallization ratio after thermal spraying and 200 kgf/cm 2  or more compression strength. A slight amount of CaO may be present to make a flame spray mending material with an oxide concentration of 89% by weight or more of SiO 2 , more than 2.0 to 5.0% by weight of CaO, 0.5 to 4.0% by weight of Na 2 O and/or more than 0.2 to 4.0% by weight of Li 2 O, and 1.0% by weight of less of Al 2 O 3 .

TECHNICAL FIELD

The present invention relates to a powdery mixture for flame spraymending as a material for mending the internal wall of an industrialfurnace, in particular, the internal wall of a coke oven in a hightemperature state by melting a powdery refractory by flame for spraymending with a spray nozzle.

BACKGROUND ART

The inside of a furnace structure as an industrial furnace, inparticular, a coke oven, a blast furnace, a steel manufacturing furnace,and the like, as the iron and steel making equipment, contacted with amolten material such as a carbonized coal, a molten iron, a moltensteel, a slug, and the like, is in a severe environment exposed to atemperature as high as 1000° C. or more. In particular, at the time ofthe coke extruding operation from a coke oven carbonizing room, or ofthe operation of injecting, storing, or discharging a molten iron or amolten steel in a steel manufacturing furnace, the internal wallexperiences a remarkable temperature change. Therefore, in the internalwall, not only a damage by melting by the penetrated molten material butalso damages including cracks and peel-off by heat spalling arefrequently encountered.

In order to cope with the various damage factors, an appropriate brickmaterial needs to be selected at the time of designing or furnaceconstruction as well as mending is required in order to prolong walllife.

For example, as the mending technology, a flame spray mending method,where a mending material is blown thermally to a refractory damage part,can be presented. The flame spray mending method is a technology where aflame spray mending material containing a mending flame resistant oxidepowder or an easily oxidizable powder, or a mixture of both, having acomposition substantially the same as that of the material of thefurnace wall refractory to be mended is thermally blown mainly to a hightemperature furnace internal wall surface. According to the method, theflame resistant oxide powder is melted by the combustion heat of acombustible gas, and the easily oxidizable powder becomes an oxide bybeing melted exothermically by its own combustion so that a spraymending layer can be formed with the flame resistant oxide powder. Inparticular, since the furnace temperature of a coke oven cannot belowered except the time of rebuilding and thus the furnace wall mendingis done as a prerequisite in a high temperature state, such a flamespray mending method is effective.

As a conventional technology concerning such a flame spray mendingmethod, for example, the method disclosed in the official gazette ofJapanese Examined Patent Publication No. 2-45110 can be presented. Themethod is a dry method comprising the steps of mixing a powdery flameresistant oxide with a combustible material and a combustible gas so asto be supplied to a combustion supporting gas containing oxygenincluding oxygen and air for thermally melting the flame resistant oxidepowder by the heat of the combustion flame and blowing the same to thedamage part of the internal wall of the furnace instantaneously. It ischaracteristic of the method that the spray mended refractory is highlydurable compared with a refractory mended by a method where a materialobtained by mixing water and a blowing material in advance so as to be aslurry is blown from a tank, that is, a wet blowing method.

As the thermal spray material to be used in such a flame spray mendingmethod, for example, a highly siliceous thermal spray materialcontaining 93.9 to 99.6% by weight or more of SiO₂, 1.5% by weight orless of Al₂O₃, 2.0% by weight or less of CaO, 1.0% by weight or less ofFe₂O₃, and 0.4 to 2.0% by weight of Na₂O is proposed in the officialgazette of Japanese Examined Patent Publication No. 3-9185. In general,this kind of material is a material having a 60% or more crystallizationratio immediately after thermal spraying where crack generationaccording to the expansion at the time of the crystallization of theamorphous (vitreous) part (<40%), and decline of the adhesion strengthcaused by the difference in the heat expansion characteristics betweenthe thermal spray mending layer and the coke oven wall bricks areobserved. That is, the material according to the above-mentionedproposal has been developed in order to overcome the problem derivedfrom the low crystallization ratio.

However, the technology disclosed in the official gazette of JapaneseExamined Patent Publication No. 3-9185 has a problem in that the thermalspray condition for having a thermal spray mending layer with a 60% ormore crystallization ratio in the material, that is, the oxygen gas flowrate, and the propane gas flow rate is limited in an extremely narrowrange. Furthermore, with the thermal spray condition capable ofobtaining a thermal spray mending layer with a 60% or morecrystallization ratio, a dense thermal spray mending layer, that is, athermal spray mending layer having a high compression strength cannot beobtained easily, and thus a problem is involved in that the wearresistance is poor and the life of the thermal spray mending layer isshort.

Moreover, as the SiO₂ material, which is the main component of theconventional thermal spray mending material, silica brick scrap is usedfrequently for reduction of the cost. However, when the brick scrap isused as the material, a lot of impurities are introduced. In particular,since CaO is a substance broadly present as a binder in silica brickproduction, CaO is introduced inevitably and thus it is difficult tolimit the amount of CaO component to 2% by weight or less. Besides,since CaO has a strong effect of lowering the crystallization ratioimmediately after thermal spraying in a SiO₂ thermal spray coat layer,the crystallization ratio needs to be improved by adjusting the othercomponents when the CaO component is present in a large amount.

As heretofore explained, problems still remained for the conventionaltechnology include tendency of crack generation in the mended layer anda low adhesion strength with respect to the base material surface. Ithas problems at least in that the need for improving the crystallizationratio is severe and the compression strength cannot be improved so thatthe wear resistance is poor and the wall life is short.

In order to improve the product crystallization ratio immediately afterthermal spraying of the flame spray mending material mainly containingSiO2, it is of course effective to eliminate a component disturbing thecrystallization, but there is a limitation for the use of a highly purematerial in view of the high material cost. For that reason,conventionally, silica brick scrap has been reused in most cases as theSiO₂ material. On the other hand, as a flame spray mending material, onehaving an 80% or more crystallization ratio immediately after thermalspraying, even in a condition where CaO is inevitably introduced fromthe silica brick scrap, and satisfying a 200 kgf/cm² compressionstrength, is required for mending a coke oven wall brick.

Accordingly, an object of the present invention is to provide a thermalspray mending material having a high crystallization ratio immediatelyafter thermal spraying and effective in dealing with a dense thermalspray mending layer in a broad thermal spray condition. Moreover,another object of the present invention is to provide a thermal spraymending material having excellent wear resistance and durability (life)by ensuring a high compression strength on one hand without the risk ofa mending layer crack or a decline in the adhesion strength with respectto the mending surface.

Still another object of the present invention is to obtain a thermalspray material capable of producing a thermal spray layer having an 80%or more crystallization ratio immediately after thermal spraying and ahigh compression strength (>200 kgf/cm²) even when CaO is inevitablyintroduced in silica brick scrap to some extent.

DISCLOSURE OF INVENTION

As the result of the elaborate study on the above-mentioned problems ofthe conventional technology, the present inventors have developed apowdery mixture as a flame spray mending material effective in obtaininga thermal spray mending layer having an 80% or more crystallizationratio immediately after thermal spraying, and having a high compressionstrength in a broad thermal spraying condition.

That is, the present invention basically is a powdery mixture for flamespray mending having an oxide concentration of 89% by weight or more ofSiO₂, more than 2.0 to 4.0% by weight of Na₂O and silica brick scrap andother inevitable impurities as the remainder. The second aspect of thepresent invention is a powdery mixture for flame spray mending having anoxide concentration of 89% by weight or more of SiO₂, 0.2 to 4.0% byweight of Li₂O and the aforesaid inevitable impurities as the remainder.The third aspect of the present invention is a powdery mixture for flamespray mending with an oxide concentration of 89% by weight or more ofSiO₂, 0.2% by weight or more of Li2O, more than 0.2 to 4.0% by weight of(Na₂O+Li₂O) and inevitable impurities as the remainder.

The fourth aspect of the present invention is a powdery mixture forflame spray mending with an oxide concentration of 89% by weight or moreof SiO₂, more than 2.0 to 5.0% by weight of CaO, 0.5 to 4.0% by weightof Na₂O, 1.0% by weight or less of Al₂O₃ and inevitable impurities asthe remainder. The fifth aspect of the present invention is a powderymixture for flame spray mending with an oxide concentration of 89% byweight or more of SiO₂, more than 2.0 to 5.0% by weight of CaO, morethan 0.2 to 4.0% by weight of Li₂O, 1.0% by weight or less of Al₂O₃ andinevitable impurities as the remainder. The sixth aspect of the presentinvention is a powdery mixture for flame spray mending with an oxideconcentration of 89% by weight or more of SiO₂, more than 2.0 to 5.0% byweight of CaO, 0.2% by weight or more of Li₂O, more than 0.2 to 4.0% byweight of (Na₂O+Li₂O), 1.0% by weight or less of Al₂O₃ and inevitableimpurities as the remainder.

In the present invention, a preferable embodiment is a powdery mixturecapable of forming a thermal spray mending layer indicating a 80% ormore crystallization ratio in the coat layer immediately after flamespraying and a 200 kgf/cm² or more compression strength.

The concentration as an oxide here stands for the amount (% by weight)of the components such as oxide, carbonate and metal remained aftereliminating the moisture contained in the material, based on the oxideas 100.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for explaining the method for measuring the adhesionstrength.

FIG. 2 is a graph showing the relationship between the Al₂O₃concentration in the material and the crystallization ratio immediatelyafter spraying.

FIG. 3 is a graph showing the relationship between the CaO concentrationin the material and the crystallization ratio immediately afterspraying.

<Reference Numerals>1 push rod 2 thermal spraying layer 3 thermalspraying nozzle 4 thermal spraying material 5 silica brick

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention contains SiO₂ as the main component. SiO₂ is thecomponent substantially the same as a silica brick used for the furnacewall internal surface of a coke oven. When the internal wall surface isa part to be mended, this is the component prerequisite forsubstantially coinciding the heat expansion characteristics of thefurnace wall brick and the thermal spray mending refractory layer.

In the present invention, the amount of SiO₂ is 89% by weight or morebased on the concentration converted to an oxide. The reason of thelimitation is that with a less than 89% by weight SiO2 amount, theamount of the impurity components inevitably introduced, such as Al₂O₃,FeO, CaO, Fe₂O3, and the like, becomes large and thus thecrystallization ratio of the mending layer immediately after thermalspraying is lowered to less than 80% by the influence. If thecrystallization ratio of the mending layer immediately after thermalspraying becomes less than 80%, cracks can be easily generated in thebonded surfaces of both according to the heat expansion differencebetween the mending layer and the furnace wall bricks at the time of100% crystallization of the thermal spray mending layer so that thethermal spray mending layer is peeled off. As the SiO₂ componentmaterial in the present invention, silica brick scrap, silica rock,silica sand, and the like, can be used.

The expression “crystallization ratio” herein denotes the sum of eachweight percentage (% by weight) of cristobalite, trydymite and quartz byquantitative analysis of the thermal spray mending layer by X-rayanalysis. The crystallization ratio can be represented by thebelow-mentioned formula

Crystallization ratio (% by weight)=cristobalite+trydymite+quartz

In general, the thermal spraying layer made of an SiO₂ material has botha crystallized part and a vitrified part generated in the layer. Amongthese, the vitrified part undergoes phase transformation by beingmaintained at a temperature of about 1000° C. inside the furnace wall soas to be gradually crystallized. Since expansion is generated accordingto the phase transformation in the crystallization process, stress isgenerated inside the thermal spraying layer to become fragile. Besides,since the adhesion between the silica brick surface to be mended and thethermal spraying layer becomes weak due to the expansion, peel-off ofthe thermal spraying layer can easily be generated on the silica bricksurface. In this context, a preferable mending material needs to have ahigh crystallization ratio immediately after thermal spraying andresistance to expansion of the thermal spraying layer even when thecrystallization of the thermal spraying layer proceeds subsequently.

According to the study of the present inventors, it was learned thatwhen the crystallization ratio of the mending layer immediately afterthermal spraying is 80%, the adhesion strength declines by about 30%when it is crystallized thereafter. And it was confirmed that the damageon the furnace wall caused by the peel-off of the thermal spraying layeris not so remarkable if the decline of the adhesion strength is 30% orless. That is, the reason the crystallization ratio after thermalspraying is set to be 80% or more in the present invention is based onthis point.

The adhesion strength here is compared by the figure in the method shownin FIG. 1, which can be sought as mentioned below.

{circle around (1)} With a push rod (a refractory having a 20×200 mmrectangular cross-section) pressed on the side surface of a silicabrick, a mending material (about 500 g) is flame sprayed below the pushrod.

{circle around (2)} The pressing force of the push rod when the thermalspray mending layer is peeled off from the silica brick by pressing thepush rod from above is measured by the below-mentioned formula and isdefined as the adhesion strength.${{Adhesion}\quad {strength}} = \frac{\begin{matrix}{{push}\quad {rod}\quad {pressing}\quad {force}\quad \left( {{kg}/{cm}^{2}} \right) \times} \\\begin{matrix}{{{push}\quad {rod}\quad {cross}\text{-}{sectional}\quad {area}\quad \left( {cm}^{2} \right)} +} \\{{push}\quad {rod}\quad {weight}\quad ({kg})}\end{matrix}\end{matrix}}{\begin{matrix}{{adhesion}\quad {area}\quad {between}\quad {the}\quad {brick}} \\{{and}\quad {the}\quad {thermal}\quad {spraying}\quad {layer}\quad \left( {cm}^{2} \right)}\end{matrix}}$

A material according to the present invention contains a predeterminedamount of Na₂O and/or Li₂O in addition to SiO₂. By having such acomponent composition, the crystallization of the thermal spray mendinglayer immediately after thermal spraying can be promoted so as to form adense and firm mending layer having a 200 kgf/cm² or more compressionstrength. If the compression strength of the thermal mending layer is200 kgf/cm², the wear resistance with respect to coke extrusion in acoke oven is sufficient as well. The above-mentioned compressionstrength is a value measured based on the testing method of thecompression strength of a flame resistant brick defined by the JISR2206. Here specimens were cut out from the thermal spray mending layerformed by thermally spraying a thermal spray mending material to thesilica brick surface by 80 mm or more thickness so as to be provided fortesting.

The amount of Na₂O, which is a component to be added, based on therefractory concentration is set to be in the range of 2.0 to 4.0% byweight. The reason thereof is that it is difficult to obtain a thermalspray mending layer having a 200 kgf/cm² or more compression strength toleave a problem in the wear resistance with less than 2% of Na₂O. On theother hand, with more than 4% by weight of Na₂O, since thecrystallization ratio of the mending layer immediately after thermalspraying cannot reach 80%, the thermal spray mending layer is easilypeeled off. A preferable Na₂O amount is 2.1 to 3.0% by weight. As theNa₂O source, sodium silicate, sodium carbonate, and the like, arepreferable but other materials can be used as well.

In a material containing more than 2.0 to 5.0% by weight of CaO, theamount of Na₂O, which is a component to be added, based on the oxideconcentration is set to be in the range of 0.5 to 4.0% by weight. Thereason thereof is that it is difficult to obtain a thermal spray mendinglayer having a 200 kgf/cm² or more compression strength to leave aproblem in the wear resistance with less than 0.5% of Na₂O. On the otherhand, with more than 4% by weight of Na₂O, since the crystallizationratio of the mending layer immediately after thermal spraying cannotreach 80%, the thermal spray mending layer is easily peeled off. Apreferable Na₂O amount is 1.0 to 3.0% by weight. As the Na₂O source,sodium silicate, sodium carbonate, and the like, are preferable butother materials can be used as well.

Li₂O is added by 0.2 to 4.0% by weight based on the oxide concentration.In general, Li₂O has the effect of improving the crystallization ratioof the thermal spray mending layer with a small amount compared withNa₂O. With a 0.2% by weight or less Li₂O amount, it is difficult toobtain a thermal spray mending layer with a 200 kgf/cm² or morecompression strength and the wear resistance is insufficient. On theother hand, with an amount exceeding 4.0% by weight, since thecrystallization ratio of the thermal spray mending layer cannot reach80%, the thermal spray mending layer is easily peeled off. A preferablerange of the Li₂O amount is 0.3 to 1.0% by weight. As an Li₂O source, amaterial such as lithium carbonate can be used.

In the present invention, when both Li₂O and Na₂O are contained, aneffect the same as or more than the above-mentioned can be achieved.That is, (Li₂O+Na₂O) is set to be in a range of more than 0.2 to 4.0% byweight. With a less than 0.2% by weight total amount thereof, it isdifficult to obtain a thermal spray mending layer having a 200 kgf/cm²or more compression strength. On the other hand, with more than 4% byweight, the crystallization ratio of the mending layer immediately afterthermal spraying cannot reach 80% and thus a problem is involved in thepeel-off of the thermal spraying layer. A range of 0.3% by weight≦(Li₂O+Na₂O)≦2.5% by weight is preferable.

When CaO is contained by more than 2.0 to 5.0% by weight, Al₂O₃ needs tobe restrained to 1% by weight or less. The reason thereof is that evenwhen the CaO amount is restrained to 5% by weight or less, unless Al₂O₃,which is a substance to lower the crystallization ratio immediatelyafter thermal spraying, is kept at 1% by weight or less, the CaO amountcontrol is meaningless. FIG. 2 shows the crystallization ratio of thethermal spraying layer immediately after thermal spraying when Al₂O₃ ischanged in a thermal spraying material containing 5% by weight of CaOand 0.5% by weight of Li₂O. The fuel gas and oxygen at the time ofthermal spraying were controlled as needed so as to have a 200 to 300kgf/cm² compression strength in each thermal spraying layer. As shown inthis figure, when 5% by weight of CaO is contained, with an Al₂O₃concentration exceeding 1.0% by weight, the crystallization ratioimmediately after thermal spraying becomes 80% or less. FIG. 3 shows thecrystallization ratio immediately after thermal spraying in the thermalspraying layer when the CaO amount is changed in a thermal sprayingmaterial containing 1% by weight of Al₂O₃. It can be learned that thecrystallization ratio of 80% or more can be maintained with 5% by weightor less CaO even if 1% by weight of Al₂O₃ is contained.

In the present invention, components other than SiO2, Na₂O and Li₂O areinevitably introduced impurities. As such components, oxides such asAl₂O₃, CaO, Fe₂O3, TiO2, K₂O can be considered. In particular, sinceAl₂O₃ has a strong tendency to disturb the crystallization, it ispreferable to have it at 1.0% by weight or less.

The grain size of the materials according to the present invention isnot particularly limited, but it is preferable to have a 0.15 mm or lessgrain size. This is because a large amount of a fuel gas and oxygen formelting the material are needed if the material grain size is coarse.

As a first embodiment of the present invention, one having thecomposition adjustment to have 89% by weight or more of SiO₂ and 2.1 to4.0% by weight of Na₂O based on the oxide concentration when 3.6 to 6.8%by weight of sodium carbonate is added to a silica material containing93% by weight or more SiO₂ can be presented. As a second embodiment ofthe present invention, one having the composition adjustment to have 89%by weight or more of SiO₂ and 0.2 to 4.0% by weight of Li₂O based on theoxide concentration when 0.5 to 9.9% by weight of lithium carbonate isadded to a silica material containing 93% by weight or more SiO₂ can bepresented. As a third embodiment of the present invention, one havingthe composition adjustment to have 89% by weight or more of SiO₂, 0.2%by weight or more of Li₂O, and more than 2.0 to 4.0% by weight of(Na₂O+Li₂O) based on the oxide concentration when 3.6% by weight or moreof sodium carbonate and lithium carbonate so as to have 3.6 to 9.9% byweight of (sodium carbonate+lithium carbonate) are added to a silicamaterial containing 93% by weight or more SiO₂ can be presented.

As a fourth embodiment of the present invention, one having thecomposition adjustment to have 89% by weight or more of SiO₂, 2.1 to4.0% by weight of Na₂O, more than 2.0 to 5.0% by weight of CaO, and 1.0%by weight or less of Al₂O₃ based on the oxide concentration when 3.6 to6.8% by weight of sodium carbonate and sodium silicate are added to asilica rock, silica brick scrap, or silica sand material containing 93%by weight or more SiO₂ is preferable. As a fifth embodiment of thepresent invention, one having the composition adjustment to have 89% byweight or more of SiO₂, 0.2 to 4.0% by weight of Li₂O, more than 2.0 to5.0% by weight of CaO, and 1.0% by weight or less of Al₂O₃ based on theoxide concentration when 0.5 to 9.9% by weight of lithium carbonate isadded to a silica rock, silica brick scrap, or silica sand materialcontaining 93% by weight or more SiO₂ is preferable. As a sixthembodiment of the present invention, one having the compositionadjustment to have 89% by weight or more of SiO₂, more than 0.2% byweight of Li₂O, 0.2 to 4.0% by weight of (Na₂O+Li₂O), more than 2.0 to5.0% by weight of CaO, and 1.0% by weight or less of Al₂O₃ based on theoxide concentration when 0.5% by weight or more of lithium carbonate andlithium carbonate so as to have 0.5 to 6.5% by weight of (sodiumcarbonate+lithium carbonate) are added to a silica rock materialcontaining 93% by weight or more SiO₂ is preferable.

The reason why sodium carbonate is used as the Na₂O source and lithiumcarbonate is used as the Li₂O source in the above-mentioned embodimentsis that sodium carbonate and lithium carbonate can be handled easily andare easily melted at the time of thermal spraying so as to be reactedwith SiO₂ easily. Further, it is preferable to mix with the materialshomogeneously.

EXAMPLES

Hereinafter the present invention will be explained specifically withreference to examples.

Example 1

The materials (grain size—0.15 mm) having the chemical composition shownin Table 1 (present invention examples) and Table 2 (comparativeexamples) were thermal sprayed by a thermal spray amount 50 kg/h by thegas flow rate (Nm³/h) shown in the same table to the furnace wall(silica brick) of a coke oven having a 750° C. furnace wall temperatureso as to form a thermal spray mending layer. The thickness of thethermal spray mending layer was about 25 mm. The thermal spray mendinglayer was collected at 3 minutes after thermal spraying and thecompression strength and the crystallization ratio by the X-ray analysiswere measured. Further, the adhesion strength with the silica brick wasmeasured at 10 minutes after thermal spraying after 100% crystallizationby maintaining the thermal spray mending layer at 1200° C. The meltingratio of the material at the time of thermal spraying was 90% or more inall the cases. The measurement results are also shown in Table 1 andTable 2.

As apparent from the above-mentioned measurement results, in a materialaccording to the present invention with the oxide concentration of (1)89% by weight or more of SiO₂, and 2.1 to 4.0% by weight of Na₂O, (2)89% by weight or more of SiO₂, and 0.2 to 4.0% by weight of Li₂O, and(3) 89% by weight or more of SiO₂, 0.2% by weight or more of Li₂O andmore than 2.1 to 4.0% by weight of (Na₂O+Li₂O), the crystallizationratio at 3 minutes after thermal spraying was 80% or more in all thecases and a 200 kgf/cm² or more compression strength was shown. Further,since these materials according to the present invention have a 80% ormore crystallization ratio at 3 minutes after thermal spraying and a 200kgf/cm² or more compression strength in a range with a ±15% or more gasflow rate of propane and oxygen, they satisfy the characteristicsrequired to a high temperature furnace wall mending material for a cokeoven. Besides, the reduction of the adhesion strength with respect to asilica brick after 100% crystallization was 30% or less in all thecases.

Example 2

The materials (grain size—0.15 mm) having the chemical composition shownin Table 3 (present invention examples) and Table 4 (comparativeexamples) were thermal sprayed by a thermal spray amount 50 kg/h by thegas flow rate (Nm³/h) shown in the same table to the furnace wall(silica brick) of a coke oven having a 750° C. furnace wall temperatureso as to form a thermal spray mending layer. The thickness of thethermal spray mending layer was about 50 mm. The thermal spray mendinglayer was collected at 3 minutes after thermal spraying and thecompression strength based on the JIS R2206 (test piece: 25 mm×60 mm×60mm) and the crystallization ratio by the powder X-ray analysis weremeasured. Further, the adhesion strength with the silica brick wasmeasured at minutes after thermal spraying after 100% crystallization bymaintaining the thermal spray mending layer at 1200° C. The meltingratio of the material at the time of thermal spraying was 90% or more inall the cases so as to eliminate the influence of the strengthdifference depending upon the melting state of the thermal spray mendinglayer. The measurement results are also shown in Table 3 and Table 4.

As apparent from the above-mentioned measurement results, when 2.0 to5.0% by weight of CaO is contained in a material according to thepresent invention with the oxide concentration of (1) 89% by weight ormore of SiO2, and 0.2 to 4.0% by weight of Li₂O, and 1.0% by weight orless of Al₂O₃, (2) 89% by weight or more of SiO₂, 0.5 to 4.0% by weightof Na₂O, and 1.0% by weight or less of Al₂O₃, and (3) 89% by weight ormore of SiO₂, 0.2% by weight or more of Li₂O and 0.2 to 4.0% by weightof (Na₂O+Li₂O), and 1.0% by weight or less of Al₂O₃, the crystallizationratio at 3 minutes after thermal spraying was 80% or more in all thecases and a 200 kgf/cm² or more compression strength was shown. Further,since these materials according to the present invention have a 80% ormore crystallization ratio at 3 minutes after thermal spraying and a 200kgf/cm² or more compression strength in a range with a ±15% or more gasflow rate of propane and oxygen, they satisfy the characteristicsrequired to a high temperature furnace wall mending material for a cokeoven. Besides, the lowering ratio of the adhesion strength with respectto a silica brick after 100% crystallization was 30% or less in thepresent invention whereas it is more than 70% in the comparativeexamples.

TABLE 1 Crystallization Adhesion strength with Gas flow ratio at respectto silica brick Chemical composition (wt %) rate 3 minutes (kg/cm²)(concentration as an oxide) (Nm³/h) after thermal 10 minutes after After100% SiO₂ Na₂O Li₂O Others* C₃H₅ O₂ spraying (wt %) thermal sprayingcrystallization Example 1 97.0 2.1 — 0.9 22 175 94 210 200 Example 296.5 2.1 — 1.4 22 175 98 250 240 Example 3 95.6 3.0 — 1.4 19 150 92 230190 Example 4 94.7 4.0 — 1.3 16 130 81 190 150 Example 5 89.0 3.0 — 8.019 150 82 170 140 Example 6 96.5 2.1 — 1.4 22 175 97 160 150 Example 798.3 — 0.2 1.5 27 215 85 200 150 Example 8 98.0 — 0.5 1.5 25 200 97 260250 Example 9 96.6 — 2.0 1.4 19 150 89 190 150 Example 10 94.7 — 4.0 1.316 130 80 200 170 Example 11 89.0 — 4.0 7.0 21 170 82 170 120 Example 1296.3 2.1 0.2 1.4 20 160 97 210 200 Example 13 95.2 2.5 1.0 1.3 17 135 86130 100 Example 14 94.7 2.1 1.9 1.3 16 130 80 180 160 Example 15 98.30.1 0.2 1.4 27 215 80 220 210 Adhesion strength by the crystallizationCompression strength Evaluation Evaluation Lowering ≦30% is ≧200 kgf/cm²is Comprehensive ratio (%) preferable (kgf/cm²) preferable evaluationExample 1 5 ∘ 1010 ∘ ∘ Example 2 4 ∘ 1150 ∘ ∘ Example 3 17 ∘ 990 ∘ ∘Example 4 21 ∘ 950 ∘ ∘ Example 5 18 ∘ 590 ∘ ∘ Example 6 6 ∘ 350 ∘ ∘Example 7 25 ∘ 330 ∘ ∘ Example 8 4 ∘ 850 ∘ ∘ Example 9 21 ∘ 790 ∘ ∘Example 10 15 ∘ 530 ∘ ∘ Example 11 29 ∘ 470 ∘ ∘ Example 12 5 ∘ 1070 ∘ ∘Example 13 23 ∘ 410 ∘ ∘ Example 14 11 ∘ 880 ∘ ∘ Example 15 5 ∘ 300 ∘ Q*Others include inevitable impurities such as Al₂O₃, CaO, Fe₂O₃, TiO₂and K₂O.

TABLE 2 Crystallization Adhesion strength with Gas flow ratio at respectto silica brick Chemical composition (wt %) rate 3 minutes (kg/cm²)(concentration as an oxide) (Nm³/h) after thermal 10 minutes after After100% SiO₂ Na₂O Li₂O Others* C₃H₅ O₂ spraying (wt %) thermal sprayingcrystallization Comparative 98.5 — — 1.5 27 200 0 62 0 example 1Comparative 98.0 0.5 — 1.5 25 200 65 100 15 example 2 Comparative 96.61.9 — 1.5 23 185 90 150 110 example 3 Comparative 94.3 4.5 — 1.2 15 12062 170 25 example 4 Comparative 87.0 3.0 — 10.0 19 150 60 120 22 example5 Comparative 98.4 — 0.1 1.5 27 215 45 85 10 example 6 Comparative 94.5— 4.2 1.3 15 120 76 42 7 example 7 Comparative 87.0 — 3.0 10.0 19 150 45170 15 example 8 Comparative 94.4 2.5 1.8 1.3 15 120 53 200 20 example 9Adhesion strength by the crystallization Compression strength EvaluationEvaluation Lowering ≦30% is ≧200 kgf/cm² is Comprehensive ratio (%)preferable (kgf/cm²) preferable evaluation Comparative 98 x 150 x xexample 1 Comparative 85 x 120 x x example 2 Comparative 27 ∘ 180 x xexample 3 Comparative 85 x 710 ∘ x example 4 Comparative 82 x 380 ∘ xexample 5 Comparative 88 x 210 ∘ x example 6 Comparative 83 x 450 ∘ xexample 7 Comparative 91 x 530 ∘ x example 8 Comparative 90 x 520 ∘ xexample 9 *Others include inevitable impurities such as Al₂O₃, CaO,Fe₂O₃, TiO₂ and K₂O.

TABLE 3 Crystallization Adhesion strength with Gas flow ratio at respectto silica brick Chemical composition (wt %) rate 3 minutes (kg/cm²)(concentration as an oxide) (Nm³/h) after thermal 10 minutes after After100% SiO₂ CaO Fe₂O₃ Al₂O₃ Li₂O Na₂O K₂O Others* C₃H₅ O₂ spraying (wt %)thermal spraying crystallization Example 16 95.2 3.0 0.4 0.5 0.2 — 0.10.6 24 190 90 280 250 Example 17 94.2 3.0 0.4 0.5 1.0 — 0.1 0.8 23 18598 350 340 Example 18 90.8 3.0 0.4 0.5 4.0 — 0.1 1.2 16 130 88 290 250Example 19 92.1 3.0 0.4 0.5 — 0.5 0.1 3.4 20 160 83 180 140 Example 2093.0 3.0 0.4 0.5 — 2.1 0.1 0.9 19 150 100 450 450 Example 21 91.0 3.00.4 0.5 — 4.0 0.1 1.0 16 130 97 320 320 Example 22 93.8 3.0 0.4 1.0 0.5— 0.1 1.2 23 185 100 400 400 Example 23 92.3 5.0 0.4 1.0 0.5 — 0.1 0.723 185 81 310 240 Example 24 92.5 3.0 0.4 1.0 — 2.1 0.1 0.9 19 150 98250 230 Example 25 89.0 5.0 0.4 1.0 — 2.1 0.1 2.4 19 150 82 240 170Example 26 94.2 3 0.4 0.5 0.2 0.7 0.1 0.9 21 170 100 330 330 Example 2789.7 3 0.4 0.5 0.2 3.8 0.1 2.3 16 130 84 270 200 Example 28 89.7 3 0.40.5 3.8 0.2 0.1 2.3 16 130 85 290 260 Adhesion strength by thecrystallization Compression strength Evaluation Evaluation Lowering ≦30%is ≧200 kgf/cm² is Comprehensive ratio (%) preferable (kgf/cm²)preferable evaluation Example 16 11 ∘ 350 ∘ ∘ Example 17 3 ∘ 500 ∘ ∘Example 18 14 ∘ 340 ∘ ∘ Example 19 22 ∘ 240 ∘ ∘ Example 20 0 ∘ 650 ∘ ∘Example 21 0 ∘ 400 ∘ ∘ Example 22 0 ∘ 470 ∘ ∘ Example 23 23 ∘ 330 ∘ ∘Example 24 8 ∘ 260 ∘ ∘ Example 25 29 ∘ 310 ∘ ∘ Example 26 0 ∘ 520 ∘ ∘Example 27 26 ∘ 410 ∘ ∘ Example 28 10 ∘ 420 ∘ Q *Others includeinevitable impurities such as TiO₂ and MgO.

TABLE 4 Crystallization Adhesion strength with Gas flow ratio at respectto silica brick Chemical composition (wt %) rate 3 minutes (kg/cm²)(concentration as an oxide) (Nm³/h) after thermal 10 minutes after After100% SiO₂ CaO Fe₂O₃ Al₂O₃ Li₂O Na₂O K₂O Others* C₃H₅ O₂ spraying (wt %)thermal spraying crystallization Comparative 95.0 3.0 0.4 0.5 — — 0.11.0 27 200 0 70 1 example 10 Comparative 93.1 3.0 0.4 1.5 — 1.0 0.1 0.920 160 47 270 20 example 11 Comparative 91.1 6.0 0.4 0.5 1.0 — 0.1 0.920 160 70 290 45 example 12 Comparative 90.0 6.0 0.4 0.5 — 2.1 0.1 0.917 135 65 350 45 example 13 Comparative 90.6 3.0 0.4 0.5 4.5 — 0.1 0.916 130 70 280 30 example 14 Comparative 90.6 3.0 0.4 0.5 — 4.5 0.1 0.915 120 76 310 90 example 15 Comparative 95.0 3.0 0.4 0.5 0.1 0.1 0.1 0.827 200 67 90 10 example 16 Comparative 88.0 6.0 0.4 0.5 0.1 0.5 0.1 0.516 130 56 250 15 example 17 Adhesion strength by the crystallizationCompression strength Evaluation Evaluation Lowering ≦30% is ≧200 kgf/cm²is Comprehensive ratio (%) preferable (kgf/cm²) preferable evaluationComparative 99 x 170 x x example 10 Comparative 93 x 250 ∘ x example 11Comparative 84 x 410 ∘ x example 12 Comparative 87 x 370 ∘ x example 13Comparative 89 x 390 ∘ x example 14 Comparative 71 x 340 ∘ x example 15Comparative 89 x 150 x x example 16 Comparative 94 x 380 ∘ x example 17*Others include inevitable impurities such aa TiO₂ and MgO.

INDUSTRIAL APPLICABILITY

According to a mending material of the present invention, since thecrystallization ratio immediately after thermal spraying is high so asto provide a dense thermal spray mending layer, the difference canhardly be found with the furnace wall brick in terms of the heatexpansion characteristics when the crystallization ratio of the thermalspray mending layer becomes 100% (at the time of expansion) so that thecrack generation or the adhesion strength decline can be prevented aswell as a thermal spray mending layer with a high compression strengthcan be obtained and thus it is excellent in terms of the wear resistanceand durability (life).

Moreover, since a dense thermal spray mending layer having a highcrystallization ratio immediately after thermal spraying can be obtainedin a material mainly containing SiO₂, including 2.0 to 5.0% by weight ofCaO and 1% by weight or less of Al₂O₃, the difference can hardly befound with the furnace wall brick in terms of the heat expansioncharacteristics when the crystallization ratio of the thermal spraymending layer becomes 100% (at the time of expansion) so that crackgeneration or adhesion strength decline can be prevented and a thermalspray mending layer having a high compression strength can be obtained.Thus, it is excellent in terms of wear resistance and durability (life).

Besides, a material of the present invention can make theabove-mentioned thermal spray mending layer with a slight amount ofoxygen gas and propane gas.

What we claim is:
 1. A powdery mixture for flame spray mending of aninterior silica brick wall of an industrial furnace, said mixturecomprising not less than 89% by weight of SiO₂, from more than 2.0 to4.0% by weight Na₂O, further comprising 0.2 to 4.0% by weight of Li₂O,and CaO containing substance and inevitable impurities as the remainder.2. A powdery mixture for flame spray mending an interior silica brickwall of an industrial furnace, said mixture comprising not less than 89%by weight of SiO₂, 0.2% by weight or more of Li₂O, and from more than0.2 to 4.0% by weight of (Na₂O+Li₂O), and CaO containing substance andinevitable impurities as the remainder.
 3. A powdery mixture for flamespray mending an interior silica brick wall of an industrial furnace,said mixture comprising not less than 89% by weight of SiO₂, from morethan 2.0 to 5.0% by weight of CaO, 0.5 to 4.0% by weight of Na₂O, 1.0%by weight or less of Al₂O₃, and inevitable impurities as the remainder.4. A powdery mixture for flame spray mending an interior silica brickwall of an industrial furnace, said mixture comprising not less than 89%by weight of SiO₂, from more than 2.0 to 5.0% by weight of CaO, 0.2% byweight or more of Li₂O, from more than 0.2 to 4.0% by weight of(Na₂O+Li₂O), 1.0% by weight or less of Al₂O₃, and inevitable impuritiesas the remainder.
 5. A product of flame spraying a powdery mixtureaccording to claim 1,2,3 or 4 onto an interior silica brick wall of anindustrial furnace, wherein said product has a crystallization ratio of80% or more, said crystallization ratio defined as a ratio ofcrystobalite, trydymite, and quartz after flame spraying, and whereincompression strength of the product is 200 kgf/cm² or more.
 6. Thepowdery mixture defined in claim 3 or 4, wherein the amount of Na₂O is1.0 to 3.0% by weight.